Correlation doesn't equal...Anyone? Anyone?

Two weeks ago, The Cavalier Daily ran an article announcing that female students who belong to chapters of the Inter-Sorority Council (ISC) had GPAs "well above" the average for all female students at the University: 3.311 compared to 3.226.

As I read, I kept waiting for the reporter to ask some hard questions about why that might be so. Instead, she drank the ISC Kool-Aid. The article quoted Sally Kline, the assistant dean of fraternity and sorority life, as attributing this "huge accomplishment" to the focus placed on the academic excellence within all the ISC sororities. Among these strategies:

For example, Kline said, "I know one [chapter] gave cookie cakes out to members who did well, and other groups do similar things."
Similarly, [ISC President Stuart] Berkeley said her sorority has a program called "Smart Cookies," which rewards chapter members with prizes for such things as not missing class or getting a good grade on an exam or paper.

Baked goods and other incentives programs are all well and good, but is it likely that membership in sororities alone explains the numbers? The academic success could actually come from another factor that simply correlates with sorority membership, but the article fails to even mention this possibility, instead simply recording the explanation offered by the ISC.

For example, take simple economics. Taking part in sorority life isn't cheap. Of the ISC sororities, only Alpha Chi Omega offers information on its membership fees on their web site. Dues come to $785 per semester there, and it's probably not a stretch to guess that the others fall within the same ballpark. With that in mind, note the ample literature documenting the basic finding that students from higher-income backgrounds, for a variety of reasons, tend to do better in college (here's an example). Given the costs of participating in sororities, one could argue that the socioeconomic make-up of the organizations play just as great a role in their higher member GPAs as any encouragement programs they offer do.

I say this not to diminish the achievement of the individual sorority members who have posted impressive, above-average GPAs but to instead repeat a mantra that news outlets so often forget when covering numbers: Correlation doesn't equal causation. The paper made the same mistake last semester with an article covering a study of so-called "helicopter" parents. The ISC probably indeed deserves credit, but by failing to mention likely alternatives, the Cav Daily probably gives them more credit than they deserve.